const fp = require('lodash/fp')
// 数据
// horsepower 马力，dollar_value 价格， in_stock 库存
const cars = [
  {name: "Ferrari FF", horsepower: 660, dollar_value: 700000, in_stock: true},
  {name: "Spyker C12 Zagato", horsepower: 650, dollar_value: 648000, in_stock: false},
  {name: "Jaguar XKR-S", horsepower: 550, dollar_value: 132000, in_stock: false},
  {name: "Audi R8", horsepower: 525, dollar_value: 114200, in_stock: false},
  {name: "Aston Martin One-77", horsepower: 750, dollar_value: 1850000, in_stock: true},
  {name: "Pagani Huayra", horsepower: 700, dollar_value: 1300000, in_stock: true},
]

let _average = function (xs) {
  return fp.reduce(fp.add, 0, xs) / xs.length
}

// let averageDollorValue = function (cars) {
//   let dollar_values = fp.map(function(car) {
//     return car.dollar_value
//   }, cars)
//   return _average(dollar_values)
// }

let averageDollorValue = fp.flowRight(_average, fp.map(fp.curry(fp.props)('dollar_value')))

console.log(averageDollorValue(cars)) // 790700